1. Field of the Invention
The present invention relates generally to burners for use in water heaters and boilers, and more particularly to a burner constructed to provide a variable heat energy output without suffering from stress cracking of the burner surface.
2. Description of the Prior Art
One typical prior art burner construction is that shown in U.S. Pat. Nos. 4,723,513 and 4,793,800 to Vallett, et al., the details of which are incorporated herein by reference. Referring to FIG. 3 of Vallett, et al., U.S. Pat. No. 4,793,800, that burner construction includes an inner screen 86 having relatively small perforations 88, and a larger outer screen 92 having relatively large perforations 90. While such a burner construction is very adequate for use in a system which is constructed to operate at a substantially constant fuel gas and combustion air flow rate to the burner, such a system is not suitable for use with varying flow rates of combustion air and fuel gas to the burner.
Some other systems have included open flame burners, much like a Bunsen burner, for use with a water heater. Examples of such systems are those seen in U.S. Pat. No. 4,852,524 to Cohen and U.S. Pat. No. 5,881,681 to Stuart.
There is a continuing need in the art for improved burner constructions, and particularly for a burner construction arranged generally like that of Vallett, et al., U.S. Pat. No. 4,793,800, but constructed in a manner suitable for varying burner heat output rates.
A burner apparatus includes a mounting head having a fuel inlet opening defined in the head for receiving combustion air and fuel gas through the opening. An inner support structure is attached to the mounting head. The inner support structure defines an interior zone communicated with the fuel inlet opening of the head. An exterior layer of flexible woven heat resistant material is received about the inner support structure and defines an exterior flame attachment surface.
Such a burner may be utilized in a water heater including a variable rate fuel supply system for supplying pre-mixed combustion air and fuel gas to the burner apparatus at a variable flow rate within a flow rate range. A heat exchanger is operably associated with the burner apparatus so that heat energy from the burner apparatus is transferred to water flowing through the heat exchanger, with the heat transfer occurring at varying rates dependent upon the flow rate at which combustion air and fuel gas are supplied to the burner apparatus.
The burner apparatus will operate at these varying heat output rates, and due to its stress free surface provided by the flexible outer layer, there will be no heat induced stress cracking of the burner.
The mounting head may include a tubular neck having a radial opening defined therethrough. An igniter is located outside of the neck adjacent the radial opening so that the igniter is proximally spaced from a combustion zone surrounding the outer layer of flexible woven heat resistant material.
The burner apparatus may include a plurality of annular foraminous back pressure baffles to balance the flow of combustion air and fuel gas along the length of the burner apparatus.
It is therefore, an object of the present invention to provide an improved burner construction capable of operating at varying heat energy outputs without creating heat induced stress cracking of the surface of the burner.
Another object of the present invention is the provision of a burner construction having an igniter located outside of the combustion zone of the burner.
Another object of the present invention is the provision of a burner apparatus having a balanced flow of combustion air and fuel gas along the length of the burner apparatus.
Still another object of the present invention is the provision of a relatively quiet operating burner apparatus.
And another object of the present invention is the provision of methods of using such burner apparatus.
Other and further objects, features and advantages of the present invention will be readily apparent to those skilled in the art upon a reading of the following disclosure when taken in conjunction with accompanying drawings.